Question

Ok, so I know there are probably a lot of errors in this code. I’m pretty new to dynamic memory allocation, pointers, etc.

The header file, account.h, is given to us by our professor. We were told not to make any changes to the .h file.

The implementation file is written by me. The main function is included just for basic initial testing. We were given another file to actually test the implementation of the account class.

If I don’t comment out the cout name line, I get a seg fault 11 error.
If I do, it’ll print the account number, but throw this error:

Test(29976) malloc: * error for object 0x62c1aa18c9d8374: pointer being freed was not allocated* set a breakpoint in malloc_error_break to debug
Abort trap: 6

Any help at all would be greatly appreciated!

Here’s the header file:

class account
{
public:
    typedef char* string;
    static const size_t MAX_NAME_SIZE = 15;
    // CONSTRUCTOR
    account (char* i_name, size_t i_acnum, size_t i_hsize);
    account (const account& ac);
    // DESTRUCTOR
    ~account ( );
    // MODIFICATION MEMBER FUNCTIONS
    void set_name(char* new_name);
    void set_account_number(size_t new_acnum);
    void set_balance(double new_balance);
    void add_history(char* new_history);
    // CONSTANT MEMBER FUNCTIONS
    char* get_name ( ) const;
    size_t get_account_number ( ) const;
    double get_balance( ) const;
    size_t get_max_history_size( ) const;
    size_t get_current_history_size ( ) const;
    string* get_history( ) const;
    friend ostream& operator <<(ostream& outs, const account& target);
private:
    char name[MAX_NAME_SIZE+1]; //name of the account holder
    size_t ac_number; //account number
    double balance; //current account balance
    string *history; //Array to store history of transactions
    size_t history_size; //Maximum size of transaction history
    size_t history_count; //Current size of transaction history
};

Here is the implementation file:

// File: account.cxx
// Author: Mike Travis
// Last Modified: Mar 3, 2012
// Description: implementation of Account class as prescribed by the file account.h

#include <cstdlib>
#include <stdio.h>
#include <iostream>
#include "account.h"

using namespace std;

//Constructor

account::account(char* i_name, size_t i_acnum, size_t i_hsize){
    string *d_history;
    d_history = new string[i_hsize];

    for(int i = 0; i<i_hsize; i++){
        name[i] = i_name[i];
    }
    ac_number = i_acnum;
    history_size = i_hsize;
    history_count = 0; 
}


account::account(const account& ac){
    string *d_history;
    d_history = new string[ac.history_size];

    for( int i=0; i<ac.get_current_history_size(); i++){
        strcpy(d_history[i], history[i]);
    }

    strcpy(name,ac.get_name());
    ac_number = ac.get_account_number();
    history_size = ac.get_max_history_size();
    history_count = ac.get_current_history_size();
}

account::~account(){    delete [] history;  }

void account::set_name(char* new_name){                 strcpy(name, new_name); }
void account::set_account_number(size_t new_acnum){     ac_number = new_acnum;  }
void account::set_balance(double new_balance){          balance = new_balance;  }
void account::add_history(char* new_history){
    strcpy(history[history_count], new_history);
    history_count++;
}

char* account::get_name() const {
    char* name_cpy;
    strcpy(name_cpy, name);
    return name_cpy;
}

size_t account::get_account_number() const{             return ac_number;       }
double account::get_balance() const{                    return balance;         }
size_t account::get_max_history_size() const{           return history_size;    }
size_t account::get_current_history_size() const{       return history_count;   }
//string* account::get_history() const{                         return *history;        }


int main(){

    account test1("mike travis", 12345, 20);
    //cout<<"\nname: "<< test1.get_name();

    cout<<"\n\nacnum: "<<test1.get_account_number()<<"\n\n";

    return 0;
}

Answer 1

In the destructor of account, you delete the history array. However, in the constructor, you allocate (and leak) an array which is stored in the local variable d_history. You presumably wanted to assign that to the member variable history instead – since you haven’t, if you get to the destructor it gives you an error saying that you’re freeing history but have never allocated it.

There’s a similar error in the copy constructor as well.

There are also other errors in your code as well, which I assume you’ll find as you go – get_name(), for example, is not going to work. I suspect the header file is not helping here, but there’s not much to be done if you’re not supposed to change that.